c++ - Unexpected results in subtraction of double in function -

i'm trying implement eigenfaces algorithm in c++. made database creation part , i'm setting recognition part.

the problem if variables correctly read file "prova.txt", once passed function odd happens: whole imd array contains values differ expected ones (i've same algorithm running in matlab reference).

i'm python programmer know it's silly c++ user, can't find errors in code (probably not optimized , full of redundancies btw). i'm posting link "prova.txt" after code.

u , omega matrices, linearized in order able pass them input arguments of function.

#include <iostream> #include <cmath> #include <fstream.h> #include <cstdlib>  using namespace std;  int confrontodb(double*, double, double, double*, double*, double*);  int confrontodb(double* test, double h, double m, double* m, double* u,                 double* omega) {   int urows = m;   int ulines = h;   double om[urows];   double imd[ulines];   double d[urows][urows];   double dist[urows];   double accum;   double minimo;   int ind = 0;    // subtract average "med" test sample "test"   (int = 0; < ulines; i++) {     imd[i] = test[i] - m[i];   }   // project "imd" on u eigenspace (om = u'*imd)   (int = 0; < urows; i++) {     (int j = 0; j < ulines; j++) {       om[i] += u[urows * j + i] * imd[j];     };   };    // generate matrix in each column copy of om   (int = 0; < urows; i++) {     (int j = 0; j < urows; j++) {       d[i][j] = om[i];     };   };    // subtract omega d   (int = 0; < urows; i++) {     (int j = 0; j < urows; j++) {       d[i][j] = d[i][j] - omega[i * urows + j];     };   };    // norm each column of d   (int = 0; < urows; i++) {     accum = 0;     (int j = 0; j < urows; j++) {       accum += d[i][j] * d[i][j];     };     dist[i] = sqrt(accum);   };    // minimum , maximum distance   minimo = dist[0];   double massimo = dist[0];   (int = 0; < urows; i++) {     if (dist[i] < minimo) {       ind = i;       minimo = dist[i];     } else if (dist[i] > massimo) {       massimo = dist[i];     };   };    cout << "minimo " << minimo << endl;   cout << "massimo " << massimo << endl;   return ind; }  int main(int argc, char* argv[]) {   ifstream f;   f.open("prova.txt");   double* omega;   omega = (double*)calloc(198 * 198, sizeof(double));   (int = 0; < 198 * 198; i++) {     f >> omega[i];   };   (int = 0; < 198; i++) {     (int j = 0; j < 198; j++) {       cout << "   " << omega[i * 198 + j];     }     cout << endl;   }    double* u;   u = (double*)calloc(4001 * 198, sizeof(double));   // float u[4001*198];    (int = 0; < 4001 * 198; i++) {     f >> u[i];   };    double* med;   med = (double*)calloc(4001, sizeof(double));   (int = 0; < 4001; i++) {     f >> med[i];   };    double* test;   test = (double*)calloc(4001, sizeof(double));   (int = 0; < 4001; i++) {     f >> test[i];   };    f.close();   cout << "etichetta riconosciuta "        << confrontodb(test, 4001, 198, med, u, omega) << endl;   free(med);   free(test);   free(u);   free(omega);   return 0; } 

link "prova.txt" (it's 13 megabytes)

expected results:

imdmatlab =    -2.5252525e-01   -1.3080808e+00   -1.8080808e+00   -2.7676768e+00   -4.1161616e+00   -3.1969697e+00   -2.5707071e+00   -2.6616162e+00   -3.1616162e+00   -2.3181818e+00   -2.1767677e+00   [...] 

with actual code, first imd element correct, second has 1/1000 error , goes randomly, these elements should enough check).